Lighting system



Patented Jan. 11, 1921.

2 SHEETS-SHEET I.

H. D. ROHMAN.

LIGHTING SYSTEM.

APPLICATION Hm) ocr. 1. 1918.

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H D. ROHMAN.

LIGHTING SYSTEM.

APPLXCATIQN FILED 0e11, 1918.

Patented Jan 11 1921.

2 SHEETS-SHEET 2.

UNITED STATES HARRY D. ROHMAN, or NEW YORK, 1v. Y.

LIGHTING SYSTEM.

Application filed @ctoher 1, 1918.

T 0 all 4.0 7mm it may concern Be it known that I, HARRY D. R HMAN, acitizen of the Republic of Switzerland, and residing at New York city,in the county of New York and State of New York, United States ofAmerica, have m vented certain new and useful Improvements in LightingSystems, (Case No. 20,) of which the following is a specification.

This invention relates to lighting systems such as used for example, inlighting and heating railway vehicles and the like. and the nature of myinvention and its objects and advantages will be best understood from abrief statement of the defects in standard systems which it is intendedto overcome.

The invention has to do primarily with the maintenance of proper voltageon the lamp or other translating circuits, while the generator is thesource of supply, and heretofore, in train lighting systems, it has beencustomary to follow one of two general methods. By one method, which ismost commonly followed, the dynamo current must pass through aresistance element. which is given such a value that the proper amountof current at the proper pressure w1ll be passed to the lightingcircuit, assuming that all of the lamps are lighted, this resistancebeing shortcircuited when the dynamo cuts out and the battery issupplying the lamps. The difficulty with this system is that it isinadequate to take care of conditions which arise out of subcontrol ofthe various lamps of the lighting circuit. In such arrangement, forexample. when one or more lamps is, or are, switched off, the ohmicvalue of the circuit is increased which occasions an increase in voltageacross the lighting circuit because of the fact that the resistanceelement now has too low a value to pass the proper amount of current atthe proper pressure, and the lamps burn too brightly and burn out veryrapidly. Similarly, if a number of lamps be added to the circuit, thenthe ohmic value of the circuit is decreased and tie voltage falls, theresistance element then having too high value to pass the proper amountof current at the proper pressure to the lighting cir cuit. It will alsobe apparent that similar fluctuations in volt ge will take place by thesubstitution of new lamps of different value place of lamps having avalue for which the stem was initially designed.

[By the other method commonly followed,

Specification of Letters Patent.

Patented Jan. 11, 1921.

Serial No. 256,381.

the lamp voltage is maintained constant by complicated regulatingmechanism which, as is well-known, does not function uniformly, unlesscarefully maintained. Vhile both systems approximate fair lamp voltageregulation, they fall short of obtaining accurate regulation. 7

It is the purpose of my invention to provide a simple and efficientmeans for obtaining very close lamp voltage regulation, and in one ofits broader aspects my invention consists, inter alia, in theutilization of a regulating resistance element, the condition of whichwill always be in uniformity, or in step, with the conditions obtainingthroughout the entire system. Further, I propose to use the batteryitself to regulate the lamp voltage.

l accomplish the foregoing, together with such oth r objects as mayhereinafter appear. by means of apparatus which I have illustrated inpreferred form in the accompanying drawings, wherein:

Figure 1 is a diagram of a lighting system reduced to its simplest formand illus trates the application of my improvements; and Fig. 2 is adiagram in which the details of the system are more fully developed.

Referring now to the simple diagram of Fig. 1, A indicates a dynamowhich is preferably of the speed controlled type such, for example, as aslipping belt dynamo in which the belt which is driven from the caraxle. slips on the dynamo pulley when the train attains a speed at whichthe dynamo develops full output, say for example, at 535 miles per hour.After this speed is attained, the armature rotates at a substantiallyconstant speed regardless of variations in train speed,

as is well understood by those skilled in this art. The battery isindicated at B, such bat tery, for the purpose of this description,being an Edison 28 cell battery. The positive and negative main leadsarerespectively indicated at '7 and 8. But one lighting circuit D isillustrated, the positive 12 of such lighting circuit being connected tothe positive 7 through the iron wire resistance r, and the negative 12being connected to negative 8. The lighting circuit is controlled by themain switch 13 and the positive 12 is also adapted to be connected tothe positive 7 by means associated with the automatic cutin and outswitch C, when the battery is supplying the lamps and the dynamo is outout. The automatic cut-in switch C may be of any preferred type and isconstructed to close when the dynamo voltage has been built up to apoint where it is equal to or greater than that of the battery, and toopen when the dynamo voltage drops below that of the battery, as is wellunderstood.

When the cutin switch is open, positive 12 is connected to positive 7,on the battery side of the cut-in switch in such manner as toshortcircuit resistance r through the me dium of contact 17, brush 16and wire 15. lVhen the cut-in switch has reached closed position, theplunger of the switch lifts brush 16 out of engagement with contact 17and the dynamo supplies the lighting circuit through resistance r. lVhenthe cut-in switch is in closed position, it also directly connects thepositive 12 to regulating wire 20 through the medium of brush 21 and contact 17, such regulating wire 20 being connected to the battery at apoint intermediate its ends. The function and the operation of theregulating wire will be clear from the following, the description beingbased on the assumption that approximately average charging conditionsobtain.

Assuming that the battery to be used in connection with the equipment ismade up of 23 Edison cells, it will require a charging voltage of 1.7volts per cell for a definite charging rate. This calls for a chargingvoltage or a generator voltage of 39 volts. Assuming now that the lampsshould burn at 31 volts; that is to say, at the voltage of the batterywhen the latter is on discharge, it will be clear that the resistance 7'must absorb 8 volts in order to operate the lamps at the proper voltage.If now one of the lamps in circuit D be switched oil, as hereinbeforepointed out, the voltage across the lighting circuit will rise andinsufiicient current will pass through resistance r to properly loadsuch resistance; 1'. .63., to bring its tempera ture to the point wherethe resistance will be such as to pass the proper amount of current atthe proper pressure.

In order to provide efficient and accurate regulation, I intend to use aportion of the battery itself as a regulating element, and to this end Iconnect the wire 20 preferably to the fifth cell from the positive endof the battery, and since each cell is at a voltage of 1.7, the dropfrom the positive to the regu lating wire will be 8.5 volts giving theregulating wire a potential of approximately volts, or substantially therequired or preferable lamp voltage. Stated in other words, I prefer toconnect the regulating wire 20 to the battery at a point where the backE. M. F. within the battery when on charge is equal to the required lampvoltage.

Assuming nowthat the cut-in switch is closed and the dynamo isgenerating a voltage sufiicient to produce a proper current in wire 12,and that wire 20 has been connected to positive 12 by brush 21, it' alamp now be switched off in circuit D, the following phenomenon willresult. The resistance through the translating circuit will immediatelyrise and be temporarily higher than the resistance through wire 20 andthat portion of the battery between said wire and the main 8, and aportion or the dynamo current, after it has passed through resistance'1, will divide, the major portion flowing to the lamps and theremainder flowing to the 18 cells of the battery, through contact 17,brush 21, and wire 20, in the direction of the arrow 22.

Since the voltage between the point where the wire 20 is connected tothe battery and the main 8 is substantially equal to the required lampvoltage, the aforementioned flow of current through wire 20 in thedircction of the arrow marked 22 will take place, n an amountcorresponding to the increase n potential across the lamp circuit, whichincrease results from the cutting out of the lamp,

Stated in other words, the Wire 20 provides a parallel path for dynamocurrent which will take the current theretofore supplied to the lamp cutout, thus maintaining the proper lamp voltage on the remaining lamps. Inthe absence of the regulating wire 20, upon increase in resistance inthe lighting circuit, there would be a drop in the current passingthrough resistance '1, but by the provision of the regulating wireproviding another path to the battery in parallel with the lamps, thecurrent flowing in the direction of arrow 22 will immediately load upthe resistance r and at once assist in reestablishing the predeterminedlamp voltage. Should an additional lamp be switched off, the completecycle of operation will again take place, with a. correspondingly largerflow in the direction of arrow 22.

Contrarywise, should the lamp current increase as, for example, by theprovision of additional lamps, it will be obvious that the regulatingwire 20 will immediately convey the necessary amount of current but inthe opposite direction, as indicated by arrow 23,

and so compensate for the insuiliciency of 1 current passing throughresistance r. Thus. the regulating wire will automatically compensatefor increase or decrease in load and maintain substantially constantpotential across the lamp circuit.

It might appear as though the foregoing arrangement would unequally,affect the cells. Thus, for example, if the current flows in thedirection of arrow 22, it will be apparent that the 18 cells of thebattery will receive a charge slightly in excess of the value receivedby the first 5 cells. This. in a measure. will be counteracted by thefact that during the cutting out of the generator, the last 18 cellswill temporarily sustain the lamp voltage until the cut-in switch isfully opened and shortcircuits resistance r. This result can be readilyachieved by properly constructing the brushes 21 and 16 and designingthe gaps between the respective brushes and the contact 17 in properproportions. This unequal charge is also counteracted by the fact thatshould the current in wire 20 flow in the direction of arrow 23, therewill be a drop in the potential across the first 5 cells, as a result ofwhich the dynamo will pass more current into the first 5 cells. However,to insure substantially uniform charge, I provide a mechanismhereinafter to be described.

In addition to the advantages of constant lamp voltage regulation, theapparatus is peculiarly advantageous as applied to certain types ofaccumulators in which there is a disposition to an abnormal gassingvoltage immediately after stopping the charge. Heretofore the lampvoltage, for a brief period, would rise because of the gassing voltageand noticeable fluctuations were inevitable. By calibrating the openingbetween brush 21 and contact 17 in such manner that current can be drawnfrom the last 18 cells for a brief period during the operation of thecut-in switch, this gassing voltage can be so reduced as to make thechanges in voltage between running and stopping substantiallynegligible. This, to a large measure, will counteract any slight excesscharge the 18 cells may have received Itwill be observed that theregulation atforded by the battery through wire 20 will always be inaccord with conditions throughout the system, because the condition 111the last 18 cells in the battery will always be in step or in uniformitywith the conditions ob: taiiiing throughout the system. Thus, if thebattery be in a low state of charge, and the cut-in switch closes whenthe dynamo voltage becomes equal to that of the battery, the voltageacross the lighting circuit will he correspondingly low, and if a lampbe switched off at such time, the regulating wire 20 will function asdescribed so as to preventflickering of the lamps. Under such conditionsthe lamps would, of course, be operated at a low voltage, correspondingto the low voltage obtaining throughout the system. and the voltagewould gradually 1ncrease as the battery again becomes charged.Flickering of the lamps, however, would be prevented by the regulatmgwlre. FllCl ing of the lamps is also prevented at the time wire 20 isconnected to wire 12 because it is preferable to make the connection ata time when the voltage across the lamp circuit 1s approximately equalto the voltage across the 18 cells of the battery. By properly designingthe cut-in switch so as to sensitively respond, this result can bereadily achieved.

In connection with the foregoing, it is to be observed that thearrangement is particularly advantageous with an Edison cell batterybecause the charging voltage rises very rapidly, the curve risingabruptly and then tapering off gradually. Thus, if the battery be welldepleted, the lamps will operate on low voltage for but a comparativelyshort period of time. \Vith batteries of other types, the voltage of thelamps will gradually increase, as before pointed out, the regulatingdevice operating to prevent flickering during low voltage periods and toprevent flickering and maintain constant potential on the lamps as thebattery approaches full charge.

Another advantage of my invention is that while heretofore in certaintypes of slipping belt train lighting systems it has been attempted toobtain lamp voltage regulation through the medium of two batteries, oneof which floats on the lamps while the other is on charge, I am. enabledto obtain eflicient regulation by the use of but a single battery andwithout the utilization of any a moving parts other than those which areessential to any lighting system.

Referring now to the complete system illustrated in Fig. 2, it will beseen that I have grouped the lamps in a plurality of suitable circuitsa, b, and 0, each circuit being adapted to be connected to the mainlighting positive 12 by means of respective switches (Z, c and f. I havealso provided a separate iron wire resistance for each circuit,respectively numbered 32, 33 and 34. These resistances are connected inparallel from the positive 7 and each resistance is given a calibrationsuch that it will pass the proper amount of current at the properpressure to its respective lighting circuit, assuming that all the lampsof such circuit are switched on. The switches (Z c and 7 and the mainlighting switch 13 connect the respective resistances, through suitablewiring, to the main lighting positive 12.

The regulating wire 20 is arranged as. before and is adapted to beconnected to main lighting positive 12 providing a parallel path for thedynamo current passing through the resistances.

As before, brush 16 serves to short circuit the lamp resistances whenthe dynamo cut out but I have provided additional brushes 25 and 26 eachconnected to the battery 120 positive through a respective resistance 27and 28. The purpose of these resistances 2? and 28 is to assist inmaintaining proper lamp voltage at the time when the dynamo. voltage hasbeen built up to the point where 25 it approximately equals the voltageof the battery at which time the cut-in switch closes but the dynamovolta e is ins flicient to pass the proper amount of current at theproper pressure through resistances 32, 33 1:30

and 34;. This apparatus is fully described and claimed in my co-pendingapplication, Serial Number 163,815, filed April 23, 1917, and for thepurposes of this specification it will sutlice to say that the cut-inswitch, after closing, is farther attracted on a rise in voltage andlifts brush 16 placing resistances 27 and 28 in parallel withresistances 32, 33 and 3 1 thereby reducing the total resistance in anamount sufficient to permit the dynamo to deliver the proper amount ofcurrent at the proper pressure to the lighting circuits. As the dynamovoltage rises, the plunger of the cut-in switch is attracted stillfarther and brush 25 is lifted out of engagement with contact 17 leavingresistance 28 in parallel with resistances 32, 33 and 34:, thusincreasing the total lamp resistance in proportion to the increase indynamo voltage. When the dynamo develops a voltage suflicient toproperly supply the lighting circuits through resistances 32, 33 and 34,the last brush 26 is lifted out of engagement with contact 17 and themain resistances 32, 33 and 34 function to maintain proper lamp voltageassuming all lamps are switched on in the respective circuits.Preferably coincident with the lifting of brush 26, regulating wire 20is connected as before described.

Resistances 32, 33 and 34 are so calibrated as to take care of the bigchanges in the lighting circuits such as the closing or opening of anyone of the switches (Z, c and f, and if any of the lamps of anindividual circuit are switched on or off, and new lamps of differentvalue substituted, or additional lamps added, the regulating wire 20will function as before set forth to maintain substantially constantlamp voltage and to eliminate flickering.

The reducer switch mechanism G and the stop charge mechanism H are fullydescribed and claimed in my co-pending application, Serial Number256,380, filed October 1', 1918, and for the purpose of thisspecification, it will suflice to point out that the reducer mechanismis designed to automatically reduce the rate of charge by placing aresistance in parallel with the battery dependent upon the condition ofthe battery as reflected by the reducer switch shunt and seriesoperating coils. The reducer 'mechanism also serves to protect thesystem against open circuit running. The stop charge mechanism Hoperates to discontinue the charge when the battery has become fullycharged. Neither the reducer mechanism nor the stop charge mechanisminterferes with the operation of the regulating wire, but all of themechanism together with the slipping belt drive constitutes an effectivelighting system.

In order to insure equal charge of all cells, I provide any suitablemechanism such as a resistance M adapted to be placed in parallel with18 cells when the main lighting switch is opened, the resistance beingcalibrated to pass but a small amperage such as would be suflicient totake care of slight inaccuracies.

It will also be apparent from the foregoing that I have provided lampvoltage regulating means of substantially zero value when there isproper voltage on the lighting circuit, such means having negative valuewhen the lamp voltage tends to rise and having positive value when thelamp voltage tends to fall. Thus the regulating element will meet all ofthe various conditions which may be encountered in train lighting andwill function uniformly, notwithstand ing the conditions in the system,because the regulating element will always be in step with suchconditions.

I claim:

1. In a car lighting system, the combinatlon of a dynamo, a lightingcircuit, a battery to be charged, a cut-in and cut-out switch in thecharging circuit, a lighting circuit resistance, a connection betweenthe lighting circuit side of said resistance and a point in the batteryintermediate its terminals, and means acting when the cut-in and cut-outswitch is closed to place said connection in parallel with the lightingcircuit.

2. In a lighting system, the combination of a dynamo, a lightingcircuit, a battery to be charged, a cut-in and cut-out switch in thecharging circuit, a connection between the battery side of the cut-inand cut-out switch, and a point in the battery interme diate itsterminals, and means acting when the cut-in and cut-out switch is closedto place the circuit through said connection in parallel with thelighting circuit.

3. In a car lighting system, the combination of a dynamo, a lightingcircuit, a battery to be charged, a cut-in and cut-out switch, alighting circuit resistance adapted to be short-circuited by the cut-inand cutout switch when the latter is open, a path in the battery inparallel with the lighting circuit and connected to the battery at apoint intermediate its terminals, and means operated by the cut-in andcut-out switch for closing and opening the circuit of the said path,said means opening the circuit to said path before the resistance isshort-circuited.

1. In a car lighting system, the combination of a dynamo, a lightingcircuit, a battery to be charged, a cut-in and cut-out switch, aresistance for the lighting circuit, a connection between the lightingcircuit side of said resistance and a point in the battery intermediateits terminals, means operated by the cut-in and cut-out switch forshort-circuiting the resistance when said switch is open, and meansoperated by the circuit through said connection in parallel with thelighting circuit.

6. In a lighting system, the combination of a constant watt dynamo, alighting circuit, a battery to be charged, a lighting circuitresistance, a connection between the lighting circuit side of saidresistance and a point in the battery intermediate its terminals, and anelectro-magnetic switch for placing the circuit through said connectionin parallel with the lighting circuit.

In testimony whereof, I have hereunto signed my name.

HARRY D. ROHMAN.

